The present invention relates to non-destructive measuring and testing systems, and more particularly to systems for scanning and mapping properties of materials.
One prior practice has been to measure thickness of a specimen of material by passing a pulse of ultrasound therethrough and measuring the time interval between reception of response echoes from the front and back surfaces of specimen. Because of the presence of interfering noise and other signals, the first and second peaks of the specimen reflected response signal are detected to determine the appropriate specimen echo response time. Peak detection depends upon the amplitude or the shape of the detected response signal, both of which can vary substantially for such response signals, making peak detection difficult and unreliable. Furthermore, since the material response generally consists of multiple echoes in the time domain, the peaks from these multiple echoes can overlap, particularly for a sufficiently thin specimen, making detection and distinction of individual peaks difficult, thereby making accurate determination of material response time difficult. Moreover, where the two peaks would overlap or nearly overlap, the two signals would interfere and displace their peaks towards each other, introducing inaccuracies into thickness measurement. Also, the relative amplitude of the second peak with respect to the first peak varies greatly from material to material, so that second peak detection is made that much more difficult.